The Choptank River basin is a mid-Atlantic coastal plain catchment which surrounds an estuarine tributary of Chesapeake Bay. Land use is dominated by agriculture (65%) and forest (26%); urban areas are small (6%), and human population density is low (30/km).A 150 year record of land use shows relatively stable patterns, with slow urbanization and net losses of agriculture and forest as human population density increased. Despite the overall stability, land use exhibited dynamic behavior, with 0.1-1%/y conversions, and modeled nutrient export increased due to application of fertilizers to agricultural lands, increased human wastewater discharges, and atmospheric deposition. These model results were supported by direct measurements over the last 40 years. As a result of the increased inputs to the estuary, algal biomass and seston have increased, and Secchi depth has decreased, indicative of encroaching eutrophication. In areas with relatively stable land use, increases in the intensity of land use (e.g., application of fetilizers, human population density) can also produce eutrophication.